Inductive reactor

ABSTRACT

An inductive reactor is described comprising an outer core body having a plurality of planar laminations of low magnetic reluctance material and a center leg spanning the hollow interior of the core body. A winding surrounds the center leg. The center leg is comprised of a plurality of parallel elongated sections extending along the length of the outer body and spaced from each other to form parallel nonmagnetic planar gaps. Each section is comprised of a plurality of elongated parallel planar strips of low magnetic reluctance material perpendicular to the planes of the laminations and the planes of the gaps.

United States Patent [72] inventor James Dao Alameda, Calif. [21] Appl. No. 38,141 [22] Filed May 18, 1970 [45] Patented Aug. 31, 1971 [73] Assignee Air Reduction Company, Incorporated New York, N.Y.

[54] INDUCTIVE REACTOR 4Claims,3Drawing Figs. [52] US. Cl. 336/83, 336/178, 336/212, 336/219 [51] Int. Cl. H011 17/06 [50] Field otSearch 336/165,

[56] References Cited 1 UNITED STATES PATENTS 613,205 10/1898 Hutin et 336/178 X 3,078,429 2/1963 Wiesner 336/219 X Primary Examiner-Thomas J. Kozma Attorney-Anderson, Luedeka, Fitch, Even & Tabin ABSTRACT: An inductive reactor is described comprising an outer core body having a plurality of planar laminations of low magnetic reluctance material and a center leg spanning the hollow interior of the core body. A winding surrounds the center leg. The center leg is comprised of a plurality of parallel elongated sections extending along the length of the outer body and spaced from each other to form parallel nonmagnetic planar gaps. Each section is comprised of a plurality of elongated parallel'planar strips of low magnetic reluctance material perpendicular to the planes of the laminations and the planes of the gaps.

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FIGS

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ing a low reluctance path of the magnetic flux produced by the current in the winding. Where DC as well as AC is carried by the winding on the core, the core steel itself is unable to absorb the DC magnetomotive force without saturation. Accordingly, where DC is to be carried in the winding, the core is generally constructed such that air gaps are placed in the magnetic flux path to increase DC reluctance and thus limit the DC magnetic flux level.

A number of problems are encountered in the manufacture of cores for inductive devices and these problems are typically compounded in the case of very large inductive reactors used for high power applications. One problem which occurs is that as DC is increased in the winding, the DC magnetic flux also increases. 1f the flux produced by the DC is not uniformly distributed in the core, localized saturation can result causing a substantial reduction ininductance.

Another problem which occurs is that of magnetic flux fringing along the air gap or air gaps in the core. Where fringing results, the effective area of the magnetic path is'undesirably varied. If the fringing flux is produced by AC, eddy current losses will result in the winding. Fringing flux problems may be substantially minimized by the use of a large number of small air gaps or nonmagnetic gaps, but this may substantially increase the .cost of the device and reduce its rigidity. Thus, forces generated by the magnetic flux in the core may create mechanical vibration and noise problems. Finally, the size of thegaps has a substantial effect on the inductance of the reactor. Thus, where precision is required,

each of the various parts comprising the reactor core have to be manufactured to precise tolerances and may require individual machining or grinding to bring them to the proper size. In the case of a large number of gaps, such procedures can substantially increase the cost of core production.

Accordingly, it is an object of the invention to provide an improved inductive reactor.

Another object of the invention is to provide an improved inductive reactor which is particularly suited to'operation at high power levels with both DC and AC current components.

It is another object of the invention to provide an inductive reactor in which the core is provided with a plurality of nonmagnetic gaps, such core being capable of manufacturing at low cost and with highly precise electrical tolerances.

A further object of the invention is to provide an improved inductive reactor which is capable of operating at very high.

power levels, such reactor having substantial mechanical rigidity and strength.

Otherobjects of the invention will become apparent to those skilled in the art from the following description, taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of an inductive reactor constructed in accordance with the invention;

FIG. 2 is a sectional view on a plane through the line 22 of gated sections 13 extending along the length of the outer body. A winding 17 surrounds the center leg. The sections 13 are spaced from each other to form a series of planar nonmagnetic gaps 14. Each section is comprised of a plurality of elongated planar strips 15 of low magnetic reluctance material, each of the strips extending the full length of the outer body and being perpendicular to both the planes of the laminations and the planes of the nonmagnetic gaps.

Referring now more particularly to the drawings, the illustrated inductive reactor is suitable for very high power applications, for example 20 kilojoules. The reactor includes the winding or coil 17 comprising a plurality of turns of a suitable electrical conductor. For example, the coil may consist of turns of No. 2 hollow copper conductor 0.465 inch X 0.505 inch O.D. 0.250 inch ID. The coil is wound around the center leg 12 and passes along either side thereof inside the outer body 11. At the ends of the inductive reactor, the winding or coil 17 protrudes slightly as may be seen in FIG. 3. The coil is separated from the outer body 11 by layers of insulation 18.

As previously mentioned, the center leg of a typical inductive reactor which may carry a DC component is constructed with at least one air gap or nonmagnetic gap therein to increase the DC reluctance and thus limit the DC magnetic flux level. To minimize the problem of fringing flux which, in the presence of AC, causes eddy current losses in the. winding, a plurality of air gaps or nonmagnetic gaps are provided. Thus, the center leg 12 of the core of the invention is provided with a plurality of nonmagnetic planar gaps 14. To do this, the center leg is comprised of a plurality of parallel elongated sections 13, each in the shape of a rectangular hexahedron. The sections extend along the length of the outer body 11 and are spaced from each other to define the nonmagnetic planar gaps. The plane of each gap may be considered as a plane bisecting the gap and parallel to the surfaces which define the gap. The planes of the gaps are perpendicular to the planes of the laminations. The center leg 12, for example, may be comprised of sections 13 which are 1 /2 inches high separated by %-inch gaps.

In order to minimize eddy current losses, cores are typically constructed of a plurality of laminations, rather than in a solid unitary structure. To this end, the outer body 11 is comprised of a plurality of planar laminations 19 arranged parallel with each other and generally perpendicular to the long dimensions of the core. Each lamination comprises a generally rectangu lar frame, as may be seen most clearly in FIG. 2. The material of the frame may be of any suitable type and is preferably v stamped out of sheet stock to the shape and dimensions desired. The plane of each lamination may be considered as a plane bisecting the lamination and parallel with the opposite largest flat surfaces thereof.

Each of the framelike laminations 19 includes a pair of projections 21 and 23 which are aligned with each other and project inwardly from opposite sides of the frame. In order to locate the center leg 12 with respect to the outer body 11, and in order to maintain proper spacing between the various sections 13 of the center leg, a support structure 25 is provided. The support structure 25 includes a pair of parallel walls 27 and 29 which extend adjacent the sides of the center leg 12 and which fit in the corner formed between the projectionsZl and 23 and the remainder of the framelike laminations 19. A plurality of shelves 31 extend between the sidewalls or panels 27 and 29 to maintain spacing between the sections 13 and thus maintain the nonmagnetic gaps therebetween. The material of which the sidewalls 27 and 29 and the shelves 31 are comprised is a nonmagnetic material which is also electrically nonconductive and of sufficient strength the withstand the forces produced during operation of the reactor. Several types of materials are capable of functioning in this manner such as polyester glass fiber manufactured by Glastic Corp., of Cleveland, Ohio. For assembly purposes, the shelves 31 may be made integral with the walls 29 and 27 but separated along the midpoint of the shelves in order that the support structure may be separated into two halves.

As previously mentioned, it is important that the dimensions of the elongated sections 13 be extremely precise in order to ensure uniform distribution of the DC magnetic flux and thereby prevent local saturation which could cause a reduction in inductance. Moreover, it is important that the dimensions be precise if large numbers of reactors of uniform characteristics are to be produced. Finally, due to the high magnetic forces produced in the core, the core should be constructed in a very rigid manner to minimize the creation of mechanical vibration and noise.

To this end, each of the elongated sections 13 is comprised of a plurality of elongated planar strips 15 of low magnetic reluctance material. Each of the strips extends the full length of the outer body 1 l and the strips are arranged perpendicular to the planes of the laminations or frames 19 and to the air gaps 14. The strips are maintained in their mutually parallel relation by the sidewalls 27 and 29 of the support structure 25, and rest on the shelves 31 thereof.

Due to the arrangement of the elongated strips 15 in mutually parallel planes perpendicular to the planes of the mutually parallel laminations l9 and the planes of air gaps 14, a very rigid structure is provided in which longitudinal bending or other types of movement which could produce mechanical vibration and noise are minimized. Moreover, it is possible to manufacture the strips to extremely precise dimensions because they may be slitted by appropriate conventional machinery to the precise dimensions required without the need for further machining, such as grinding. Thus, the machining typically required for manufacturing a core is eliminated, and it is possible to manufacture a large number of cores of very uniform properties without the need for additional finish machining of the parts. Slicing or slitting machinery is available and well known in the art and is capable of slicing or slitting the strips to within 0.001 inch tolerance at very little cost. This is opposed to stamping the pieces and subsequently sawing or grinding them to size as is often done in manufacturing cores of more conventional design. For example, several thousand of the strips 15 may be readily manufactured to within 0.00] inch tolerance, thereby providing a high degree of uniformity for a plurality of cores. Moreover, because of the arrangement of the strips, running lengthwise to the body 11, the strips act as beams which greatly increase the stiffness of the assembly. For example, the sectional modulus of each strip may be as high as 1X10", with a corresponding sectional modulus in the entire elongated section 13, a substantial improvement over more conventional art designs.

It may therefore be seen that the invention provides an improved inductive reactor in which assembly costs are minimized, dimensional tolerances are substantially improved, ans mechanical rigidity is substantially increased. Thedesign is relatively simple from a constructional standpoint and enables the production of a large number of identical reactors I with properties which are very close and uniform. The invention provides a substantial cost reduction over more conventional or known prior art constructions.

Various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and accompanying drawings. Such modifications are intended to fall within the scope of the appendant claims.

What is claimed is:

1. An inductive reactor, comprising, an outer body of low magnetic reluctance material forming an elongated hollow structure, said outer body being comprised of a plurality of planar laminations arranged parallel with each other, a center leg spanning the hollow interior of said outer body and extending along the length thereof, and a winding on said center leg, said center leg being comprised of a plurality of elongated parallel sections extending along the length of said outer body, said sections being in the shape of rectangular hexahedrons and being spaced from each other to form a series of nonmagnetic planar gaps, said sections each being comprised of a plurality of elongated parallel planar strips of low magnetic reluctance material, each of said strips extending the full length of said outer body and being perpendicu ar to the planes of said laminations and the planes of said gaps.

2. An inductive reactor in accordance with claim 1 wherein each of said laminations comprises a generally rectangular frame.

3. An inductive reactor according to claim 2 wherein each frame includes a pair of projections aligned with each other and projecting inwardly from opposite sides of said frame, and wherein a nonmagnetic support structure is provided supporting said center leg, said support structure engaging said projections on said frames.

4. An inductive reactor according to claim 3 wherein said support structure comprises a pair of parallel walls and a plurality of shelves extending perpendicular to said walls for separating said elongate sections of said center leg. 

1. An inductive reactor, comprising, an outer body of low magnetic reluctance material forming an elongated hollow structure, said outer body being comprised of a plurality of planar laminations arranged parallel with each other, a center leg spanning the hollow interior of said outer body and extending along the length thereof, and a winding on said center leg, said center leg being comprised of a plurality of elongated parallel sections extending along the length of said outer body, said sections being in the shape of rectangular hexahedrons and being spaced from each other to form a series of nonmagnetic planar gaps, said sections each being comprised of a plurality of elongated parallel planar strips of low magnetic reluctance material, each of said strips extending the full length of said outer body and being perpendicular to the planes of said laminations and the planes of said gaps.
 2. An inductive reactor in accordance with claim 1 wherein each of said laminations comprises a generally rectangular frame.
 3. An inductive reactor according to claim 2 wherein each frame includes a pair of projections aligned with each other and projecting inwardly from opposite sides of said frame, and wherein a nonmagnetic support structure is provided supporting said center leg, said support structure engaging said projections on said frames.
 4. An inductive reactor according to claim 3 wherein said support structure comprises a pair of parallel walls and a plurality of shelves extending perpendicular to said walls for separating said elongate sections of said center leg. 